fix(backend): use duration instead of timestamp for auth cookie maxAge (#5821)

The maxAge option in Express's res.cookie() expects a duration in milliseconds, not an absolute timestamp. The previous code was adding `Date.now()` to the validity period, causing cookies to expire decades in the future instead of the intended 1 day / 7 days.

This was particularly problematic on macOS due to stricter cookie handling by Safari/WebKit.

Addresses #5818

Co-authored-by: njg7194 <njg7194@users.noreply.github.com>

packages/hoppscotch-backend/src/auth/helper.ts

@@ -58,13 +58,13 @@ export const authCookieHandler = (
     httpOnly: true,
     secure: configService.get('INFRA.ALLOW_SECURE_COOKIES') === 'true',
     sameSite: 'lax',
-    maxAge: Date.now() + accessTokenValidityInMs,
+    maxAge: accessTokenValidityInMs,
   });
   res.cookie(AuthTokenType.REFRESH_TOKEN, authTokens.refresh_token, {
     httpOnly: true,
     secure: configService.get('INFRA.ALLOW_SECURE_COOKIES') === 'true',
     sameSite: 'lax',
-    maxAge: Date.now() + refreshTokenValidityInMs,
+    maxAge: refreshTokenValidityInMs,
   });
 
   if (!redirect) {